The ins and outs of necrotic enteritis

The gastrointestinal tract of commercial poultry is constantly exposed to a wide variety of potentially harmful factors which can have a detrimental impact on flock health and productivity. Poultry production is becoming ever more challenging. The drive to reduce antibiotic usage has intensified. Maintaining gut health will therefore become increasingly important for farmers when it comes to securing a competitive advantage.

The costly intestinal disease, necrotic enteritis (NE), has severe consequences for gut health. Recently, NE has re-emerged as one of the most serious diseases of commercial poultry, prompting producers to consider whether there is more they could be doing to maximize their flock’s productivity.1

Bad news for farmers’ bottom line
Necrotic enteritis (NE) is a potentially devastating intestinal disease of broilers, layers and turkeys caused by the toxin-producing bacteria, Clostridium perfringens (C. perfringens). The bacteria are classified into five types (A–E), based on the production of different toxins. Type A isolates, and occasionally type C, are most often associated with NE and their toxins are able to destroy the intestinal lining.1 This allows the toxins to enter the bird’s bloodstream and damage other organs, such as the liver. Ingestion of virulent strains of the bacteria from the environment, especially from fecal content, is thought to be the most common route of infection.2
Although birds from between two weeks and six months of age can be affected, likelihood of disease depends on the type of bird and rearing conditions. For example, broilers raised on litter will typically be affected between two and five weeks of age, whereas layers raised on floor pen systems are often affected between three and six months of age.1,2
Infection can either result in acute, clinical disease or manifest as a more chronic, subclinical problem. In acute disease, typically there is a sudden increase in flock mortality, often without warning, with up to one percent of the flock dying per day. Although most commonly described in relation to broilers, the consequences of NE are just as severe for layers, where sudden death can occur with, or without, a noticeable drop in egg production. Other signs include those common to most intestinal diseases including depression, dehydration, anorexia, diarrhea and ruffled feathers.1 The signs are usually short-lived, as birds tend to die quickly.

The flock history, along with post-mortem examination and microscopic examination of gut contents, is usually sufficient to make a diagnosis. On post-mortem inspection of the small intestine, the inner lining of the gastrointestinal tract is usually dead (necrotic), signs of coccidiosis may be present and a brown, foul-smelling fluid may be found.2

It is the chronic, subclinical form that often goes undetected, causing large reductions in growth and feed conversion rates, and is therefore the largest cause of economic loss. In addition, liver condemnations at the processing plant are also not uncommon with the chronic, subclinical form of the disease. With such far-reaching effects, it’s perhaps not surprising that NE is thought to cost the industry around $2 billion globally.1

Gut health – the key ingredient
C. perfringens occurs naturally in the gastrointestinal tract of chickens and is ubiquitous in the environment, being present in soil, litter, water and feed. Colonization of the gastrointestinal tract is thought to occur as early as the day of hatch.1 In robust, healthy chickens the bacteria can be present in the birds’ intestines without causing any harm. So why does the bacteria cause disease in some birds and not others?

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